It's a cold morning, crisp with the breath of impending winter, but Valley Creek defies ice and gurgles on.
For decades this prime trout stream in Washington County dumped tons of sediment and contaminants into the scenic St. Croix River near Afton. But no more. After extensive work this summer and fall to repair nature's excesses, managers of the Valley Branch Watershed District hope to slow erosion on Valley Creek, improve the trout's spawning habitat and ease pollution in the river.
"If you don't manage water resources you're never going to improve water quality," said John Hanson, the watershed district's engineer, during a visit to the creek Friday.
Most of Valley Creek weaves through private land, raising occasional questions about why the watershed district spent about $385,000 on two projects, collectively known as the Valley Creek Repair and Rehabilitation Program, to control runoff and to make sure the creek doesn't eat away at the land.
The creek is one of 13 trout streams in the metro area. It sustains large populations of brown and rainbow trout and also brook trout, the only trout species native to Minnesota.
"It's unique enough that we have to preserve it," said Afton resident Don Scheel, who's secretary of the watershed district. "Some things you have to preserve by keeping people away."
The ultimate question is how much Valley Creek has contributed to phosphorous contamination of Lake St. Croix, which landed on Minnesota's impaired-waters list for the first time last year. The lake, where the river runs wide and deep from Stillwater south to Prescott, Wis., absorbs water from dozens of tributaries.
In the big picture, Valley Creek is but a trickle into the St. Croix, said Craig Affeldt, a scientist at the Minnesota Pollution Control Agency. Determining how much contaminant-laden sediment the little creek carried into the big river would require more guesswork than scientific analysis, he said.
Valley Creek is one of 23 significant tributaries that are being monitored to determine how they might be contributing to the St. Croix's impairment, Affeldt said.
Despite Valley Creek's hungry appetite for sediment -- about 1,400 tons a year had washed into the St. Croix before the restoration began -- the creek was never listed as impaired, he said. "It's been kind of a magnet for research," he said of Valley Creek. "It's a project we like to show off."
Much of the Valley Creek watershed, 9,091 acres in size, remains undeveloped. It's not a long stream -- the main branch of the creek flows 3.4 miles from Lake Edith to the St. Croix River. Hanson and Scheel, standing beside the creek one morning last week, talked about the engineering methods -- which Hanson designed -- that discourage water from chomping away at the sandy soil.
One of those projects involved building an infiltration basin on Oakgreen Avenue that cost about $135,000. This half-acre basin prevents water from eroding a ravine that drains into Valley Creek's south fork. Runoff had carried an estimated 24 tons of sediment to the creek each year. A second phase of this project will stabilize the ravine.
The other project, costing about $250,000, improved water flow downstream. A method known as channel shaping, where clusters of small boulders guide the flow of water toward the center, was used to stabilize 4,700 feet of the creek. This raised the channel bottom and reduced the potential for erosion, the watershed district said.
The district received about $150,000 in federal grants for the work. The rest came from property tax revenue in the watershed district, which extends west almost to Woodbury.
Scientists who evaluate Lake St. Croix data say that phosphorus has settled in that portion of the river because it's far deeper -- from about 40 feet to 70 feet in some places -- than the rest of the river. Phosphorous contamination that landed the federally protected St. Croix River on the impaired-waters list has been building for decades, experts familiar with the river have said.
One of them, Affeldt, said that large algae blooms in Lake St. Croix have resulted from excessive phosphorus, which can alter a river's ecosystem. Phosphorous usually comes from urban lawn runoff, stormwater discharge, farm fields and septic systems.
To Scheel, a former mayor in Afton, the restoration of Valley Creek means an investment against hard rains and severe flooding.
"I think this is incredible," he said. "It's going to be really nice and serve a useful purpose."
Kevin Giles • 651-298-1554